The Research On Anti-Collision Problem Of Radio Frequency Identification (RFID)

Radio Frequency Identification (RFID) is a kind of non-touching automatic identifying technology. It can automatically identify the target and get information through radio-frequency signal. RFID has unexampled advantages compared to barcode, such as reading information directly without touching; working under bad environment; the better penetrability and identifying more objects simultaneously. As one applied technology, it's immature yet, and still has some shortcomings, like the poor accuracy rate of identifying, the slow progress of RFID standardization, etc. Among those elements, in the dense environment due to tag-collision and reader-collision problem, the lower efficiency of system will become bottleneck to the RFID technology's application and promotion. Therefore finding a fast, accurate and reliable solution to solve the anti-collision problem is of very important significance in developing the RFID technology.The main contents of this thesis are about the research on anti-collision algorithm of RFID systems, including tag's and reader's. According to the anti-collision problem of multi-tags communication Within the reading range of a single reader, the paper combine with RFID standard (mainly UHF frequencies as EPC Gen2 and ISO18000-6), and detailedly discuss ALOHA algorithm and Binary tree search algorithm along with algorithms which improved from them. Besides the performance of advantages and disadvantages and their application situation are also analyzed. Based on those work, an improved Dynamic Frame Slotted ALOHA algorithm is put forward. The proposed algorithm compared to conventional ones, when there are a large number of tags in the field, can achieve high system efficiency by grouping to restrict the number of unread tags. Simulation results show that the proposed algorithm improves the slot efficiency above 80% at least compared to the conventional algorithms when the number of tags reach 1000.Otherwise, the anti-collision problem with respect to the environment of multi-readers, although it's similar to the Frequency Assignment Problem experienced in cellular telephone networks, but RFID system has its own unique features, like tag interference due to the lower functionality of tag and the practical system operating constraints. Making reference to domestic and foreign literature, several types of readers collision are defined and analyzed, moreover utilizing graph coloring theory to establish collision model of readers. Subsequently, both Colorwave and HiQ algorithm which used to solve the problem of reader-collision are discussed in detail, and it will pave the way for future research on those more complicated problems, like the communication between multi-tags and multi-readers, and the communication process of mobile reader device etc.